This invention relates to the preparation of dialkyl adipate, by the carboalkoxylation of butadiene.
The preparation of dialkyl adipate by the reaction of carbon monoxide and a lower alkyl alcohol with butadiene in the presence of cobalt catalysts and teritiary nitrogen base cocatalysts, i.e., pyridine, is known --see, for example, Kummer, et al U.S. Pat. No. 4,169,956, and Bruner, et al U.S. Pat. No. 4,570,016. The Kummer, et al process produces the diester by two reactions; first, producing the mono ester, i.e., alkyl 3-pentenoate, then separating a portion of the pyridine, and then reacting the alkyl 3-pentenoate to form the dialkyl adipate. The Bruner, et al process also employs two reactions, and between the reactions, the cobalt catalyst is regenerated by contact with a strongly acidic ion exchange resin.
Kummer, et al U.S. Pat. No. 4,169,956 discloses at Column 5 line 27 the addition of hydrogen to the reaction mixture of pentenoic acid ester, carbon monoxide and alcohol to increase the rate of reaction.
German Pat. No. 1,618,156 to BASF discloses the reaction of ethyl 3-pentenoate with carbon monoxide and an alcohol to form acid esters using a cobalt catalyst, pyridine cocatalyst, in the presence of water --see Example 8--to form diethyl adipate.